A conventional type linear motor has such structure that a rotating machine is cut open and great attraction acts between a mover including a row of magnets and an armature. Therefore, a great load is applied to a member that supports the mover and the ripple of force is caused at an end of the armature because of the discontinuity of a magnetic circuit.
Vibration and noise are caused by the ripple of force and a load onto a supporting part increases. Besides, a problem that the positioning accuracy of the linear motor is deteriorated because of the ripple of force also occurs.
Then, a method of reducing the ripple by providing an auxiliary magnetic pole at the end of the armature and diagonally arranging the auxiliary magnetic pole is taken as disclosed in a patent literature 1. According to this patent, as the ripple is offset by providing the auxiliary magnetic pole at both ends of the armature and diagonally arranging the auxiliary magnetic pole, the nonuniformity of thrust can be improved.